Effective treatment and decolonization of a dog infected with carbapenemase (VIM-2)-producing Pseudomonas aeruginosa using probiotic and photodynamic therapies

Abstract

Background – Carbapenem-resistant bacterial infections are a critical problem in veterinary medicine with limited treatment options. Objective – To describe effective probiotic and photodynamic therapy of a dog with gut colonization and ear infection caused by a hospital-associated lineage of carbapenemase (VIM-2)-producing Pseudomonas aeruginosa. Animals – A 5-year-old Lhasa apso dog presented with otitis externa. Methods and materials – Unilateral otitis externa caused by carbapenem-resistant P. aeruginosa was treated with antimicrobial photodynamic therapy (aPDT) using methylene blue as photosensitizer [wavelength 660 nm, fluence 140 J/cm2, 8 J and 80 s per point (six equidistant points), 100 mW, spot size 0.028 cm2 and fluence rate 3.5 W/cm2]. The isolated bacterial strain also was tested for susceptibility to in vitro aPDT where the survival fraction was quantified by colony forming unit counts after exposure to increasing light doses. For decolonization, probiotic supplements were orally administered (once daily) for 14 days. Effectiveness of probiotics and photodynamic therapy was evaluated by clinical and microbiological culture assays. Results – Complete resolution of clinical signs was achieved by Day 7 after aPDT. Samples collected immediately and after seven and 14 days following aPDT were negative for VIM-2-producing P. aeruginosa. Oral and rectal swabs collected on days 7, 14 and 21 after probiotic therapy, confirmed effective gastrointestinal decolonization. Conclusions and clinical importance – Combined use of aPDT and probiotics could be a promising therapeutic strategy for treatment of superficial infections produced by carbapenem-resistant bacteria, while avoiding recurrent infection due to intestinal bacterial carriage of these multidrug-resistant pathogens.